Stories where Spike and Buffy have children or Dawn is their blood child.
Stories written without canon characters involved
Stories that include all the seasons or a variety of seasons.
Stories that happen in the NCIS universe or use NCIS characters
Stories that bring the BTVS/ATS characters in contact with characters from other fandoms.
Any kind of universe that might veer from the normal canon.
Short scenes that are not connected together, for the most part.
Stories that have nothing to do with BTVS/ATS and are in a different fandom without crossing over to Buffy.